In recent years, IEEE 802.11a/g/b-based wireless LANs have become common for home use. Higher speed wireless standards are also under development. In the industry, there are trends to place wireless LANs as home network infrastructure by the distribution of AV streams using a high-speed wireless LAN, a home security sensor (glass breakage detection) using the easiness of wireless installation, and the like.
Meanwhile, due to characteristics of radio waves, wireless LANs are susceptible to blocking objects, noise caused by electromagnetic waves, and the like. Particularly, millimeter waves, UWB, etc., for high-speed wireless LANs are susceptible to obstacles and the like. In order to spread high-speed wireless LANs as home network infrastructure, there is a need to take measures against such interference.
However, wireless LANs are premised on an ad-hoc connection (which is not continuous communication but a dynamic network connection). Thus, wireless disconnection is not recognized as an abnormal condition. The IEEE 802.15.3 standard and the like do not even consider a mechanism for treating wireless disconnection as an abnormal condition. Also, there is no mechanism for notifying communication disconnection in a wireless network layer. Particularly, in the case of a network where a wired portion is tunneled (an IP packet or Ethernet frame is encapsulated), a device on the Ethernet side considers wireless disconnection as an unexplained communication failure.
The development of the high-speed wireless LAN is still at an experimental stage towards the practical use. In current measures, circumventing measures from the viewpoint of devising strategies for prevention of radio interference, such as “sending radio waves from a location with a clear view using a waveguide” or “appropriately adjusting an output” is mainstream.
As a conventional technique, Japanese Unexamined Patent Publication (Kokai) No. 2004-282758 discloses a method in which, in a wireless network which is controlled by a single controller, when the controller breaks down (or stops) the controller is switched to an alternative controller and network control is performed using the alternative controller, whereby the wireless network is maintained. However, this method is not to circumvent a situation where wireless communication becomes difficult under the influence of a blocking object, noise caused by an electromagnetic wave, or the like.